Impedance based damage assessment of concrete under the combined effect of impact and temperature using different piezo configurations

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The concrete structures undergo severe damage under the impact loading, which may cause further fatal casualties to life and property and these damage become more dangerous as the temperature rises. This is controlled by performing the proper structural health monitoring (SHM) of structures. In recent years, the electromechanical impedance technique (EMI) has emerged as a promising method for monitoring the health of concrete structures. The objective of this study is to determine the damage in concrete under the impact and thermal loading circumstances using the EMI technique. For this purpose, an experimental study was conducted to investigate the effect of impact loading on concrete at varying temperatures using different piezo sensor configurations. The concrete cube was tested for three piezo sensor configurations, bonded, non-bonded and embedded with a lead zirconium titanate (PZT) patch. A free-falling iron ball was dropped from a fixed height above the top surface of the test samples to simulate the impact loading. Temperature heating was performed using the oven for each concrete cube at 50 °C, 100 °C and 150 °C. The impedance measurement device was used to acquire the signatures from the piezo sensors. Statistical parameters such as root mean square deviation and mean absolute percentage deviation were calculated from the signature, demonstrating a high degree of damage detection under the impact loading at higher temperatures. These signatures are also used to determine the PZT equivalent system parameters (damping, stiffness, and mass) of the specimens under various damage conditions, as well as to establish the remaining life of the model. The study revealed that the EMI technique in SHM is capable of accurately assessing damage under impact loading at rising temperatures. Although all three sensor configurations are capable of detecting damage but, the study shows that the embedded sensors provide more accurate results.